The present invention relates to apparatus for removing liquids from strips of photographic material or the like. More particularly, the invention relates to improvements in apparatus for removing liquid films and/or droplets from moving strips or webs which issue from liquid baths.
A developing machine for exposed photographic films includes a plurality of receptacles each of which contains a different liquid bath and rolls or analogous means for guiding and transporting exposed film strips seriatim through successive baths. The machine is normally designed for treatment of film strips having different thicknesses and/or widths. The receptacles contain liquids which perform a developing, fixing, bleaching, washing and/or other function. Recent types of developing machines further comprise intercepting devices or apparatus which prevent the moving strip from entraining liquid films or droplets from a preceding receptacle into the next-following receptacle. Removal of liquid films or droplets which adhere to the sides of a moving strip is desirable and often necessary because the baths contain different chemicals which, when introduced into the next-following receptacle or receptacles, could change the consistency of the respective baths and adversely influence the developing process. Each bath is intended to contact successive increments of the moving strip for a given period of time which is considered necessary to insure an optimum treatment of the strip in the respective receptacle. The length of intervals during which a given increment of the moving strip is held in contact with a particular liquid depends on the length of the path portion along which an increment of the strip moves during travel through a bath as well as on the speed of lengthwise movement of the strip. As a rule, the speed of the strip is constant or nearly constant so that the influence of chemicals upon the strip can be changed by changing the concentration or nature of chemicals in the receptacles and/or by changing the length of that portion of the path for the strip which extends through the contents of a receptacle. Under normal circumstances, the concentration of chemicals in various receptacles of the developing machine remains or should remain constants, i.e., it should change only as a result of interaction between such chemicals and the moving strip. The developing machine comprises means for suppling to the receptacles fresh liquids at regular or irregular intervals as well as means for regenerating the liquids which are withdrawn from certain receptacles. The extent to and the frequency at which the liquid in a given receptacle must be regenerated depends, among others, on the quantity of liquid which the moving strip removes from the receptacle and also on the quantity of liquid which the sides of the moving strip entrain into such receptacle from the preceding receptacles. In most instances, the quality of liquid in a given receptacle undergoes rapid and radial changes if the strip is permitted to introduce substantial quantities of liquid from the preceding receptacle or receptacles.
The aforedescribed conventional intercepting devices or apparatus for preventing the transfer of liquids from preceding into the next-following receptacles of a developing machine are not entirely satisfactory because they are incapable of removing sufficient quantities of liquid and/or because they are likely to scratch or otherwise deface or damage the moving strip. The conventional intercepting apparatus are normally mounted in regions where successive increments of a moving strip emerge from the liquid baths so that the intercepted liquids can be readily returned into the respective receptacles. Moreover, such mounting of the intercepting apparatus insures that the liquid in the next-following receptacle or receptacles can act upon successive increments of the strip as soon as such increments enter the liquid bath or baths; this will be readily understood since the liquid in a second bath can come into immediate contact with both sides of the moving strip if the sides were relieved of surplus moisture and eventually allowed to dry prior to entry into the next bath.
In accordance with a presently known proposal, the liquid intercepting apparatus is mounted upstream or ahead of the last guide roll for the film strip in a given receptacle of the developing machine. The intercepting apparatus includes a fixedly mounted bracket for two elastic liquid-intercepting members which are mounted on the bracket opposite each other so as to engage and wipe the respective sides of the moving strip. The moving strip flexes the lips of the intercepting members so that lips form a narrow passage whose width decreases in the direction of movement of the strip. A drawback of such devices is that the pressure with which one of the lip bears against one side of the moving strip equals or closely approximates the pressure with which the other lip bears against the other side of the strip only when the strip is guided with a very high degree of accuracy, i.e., when successive increments of the strip do not move sideways from a predetermined path. This can be achieved only when the developing machine is to process single type of strips. If the thickness and/or width of strips varies, successive increments of the strips are likely to move sideways from the predetermined optimum path so that liquid-intercepting action of one lip is much more pronounced than that of the other lip. The aforementioned last guide roll is normally formed with a concave peripheral surface so that a relatively narrow film moves closer to its axis than a relatively wide film; consequently, the path along which a wide strip advances through the liquid intercepting station deviates from the path for a relatively narrow film. Another reason for deviations of the path along which the strip moves through the liquid intercepting station from an optimum path is that the strip exhibits a tendency to flutter during movement from a preceding guide roll toward the next-following guide roll. The fluttering becomes more pronounced when the strip must move along or through an obstruction which tends to retard or brake its lengthwise movement and the braking or retarding action of such obstruction is thereupon terminated abruptly rather than gradually.